When using Productivity Tools to schedule a meeting from Outlook, the registration option is grayed out.
Cisco Webex Meetings Desktop App disables the Registration tab when scheduling Webex Meetings.
It is currently not possible to register with Productivity Tools, but it will be available in the future through Webex.
Registration is disabled in Outlook when you schedule a meeting using Productivity Tools:
Instead of receiving a link to register for a meeting, participants will receive an email inviting them to join.
It is recommended that you use the Advanced Scheduler to schedule your meeting so that registration is enabled for your meeting.
Here is an article on scheduling Cisco Webex meetings in modern view that you may find helpful